Source: Rama Nama
When ‘RA- MA’ and ‘A’-‘U’-‘M’ pronounced, they sound similar.
Rama Nama is considered equivalent to the Pranava Mantra.
Rama Nama is accorded the same power and potency in Bhakti Shastras as is accorded the Pranava Mantra in Vedanta Shastras.
Please check these: Excerpts from a discourse by our Sri Sri Muralidhara Swamiji